Common loudspeaker equipment is shown in FIG. 22 in full-range loudspeaker unit use and an enclosure formal cabinet, furthermore FIG. 23 shows generating of sound and the vibrational state of a loudspeaker unit and the vibrational state of the cabinet by vibration of the vibrating cone of a loudspeaker unit, and the direction of an arrow of the figure is shown in the state in case the vibrating cone operates ahead by plus polarity, and FIG. 24 shows the schematic drawing the vibration propagation process. The loudspeaker system is established by the vibrating cone anteroposterior vibration of the loudspeaker unit by Fleming's left-hand rule between the magnetic field of the loudspeaker magnet and the magnetic field of the voice coil of the loudspeaker input signal, on the base of the stationary point of the non-vibration, and, thereby, a realistic reproduction sound of high resolution can be obtained. Especially for this high resolution, there is also a historical background needs of high-resolution sound that has been growing in an era of image is high resolution and has become a full high-definition video.
However, the loudspeaker unit of the loudspeaker system is a vibration generator, sound emission by the vibration of the loudspeaker vibrating cone is a purpose, and the loudspeaker frame and the all panels of the cabinet should be a stationary point of the non-vibrating, but the vibrating cone unit vibrates vibration accompanying occurs with adverse effect these vibrations are superimposed on the generated sound from the vibrating member of the loudspeaker unit direct sound emission from a cabinet is also made. With the sound generation of the air vibrations P1 forward due to vibration of the loudspeaker vibrating cone SPa, the vibration of the loudspeaker frame SPd through the loudspeaker damper SPb or loudspeaker edge SPc is generated specifically, the loudspeaker cabinet according to the frame vibration P3 of the front baffle 1a occurs. By complex of the air transmission of the rear air vibration P2 due to the vibrating cone vibration of the loudspeaker unit, and the solid propagation of the vibration of the front baffle, the surplus vibration P4 each side of the cabinet 1b•1c•1d occurs further. In addition to these, the resonance by the cabinet wall reflection is added, the vibration P5 flocks to vibrating cone backside of the loudspeaker unit again, then it makes the surplus vibration to the vibrating cone SPa, and the sound passes through the vibrating cone SPa. There is a vibration P6 of the reverse phase of the magnet side by the action and reaction of the vibration of the vibrating cone SPa of the loudspeaker unit in addition to this, this is work in momentum conflicting back and forth movement of the vibrating cone. The loudspeaker system serves as a sound generation, including also the variety surplus vibrations, and these caused the superimposition of distortion and sound masking fine sound to the air vibration P1 forward due to vibration of the vibrating cone SPa, therefore a fundamental and comprehensive solution for the removal of surplus vibration of all these is requiring.
For the cabinet and the loudspeaker unit is a two major elements of the loudspeaker system, proposal of material structure and many have been made so far, is an example of the loudspeaker cabinet to suppress the vibration by forming a reinforcing rib of the mountain-shaped cabinet rear panel vibration reduction of the cabinet (see for example, Patent Document 1), there is produced a composite baffle plate which inserted a viscoelastic sheet having airtightness large vibration damping effect a loudspeaker cabinet to suppress, such as rubber (see for example, Patent Document 2). The suppression of vibrations radiation consists of laminate obtained by laminating damping alloy (see for example, Patent Document 3), and resin plate box, and wood brittle material stone, concrete, ceramic, with silica fume mortar, plastic, and viscosity, such as iron, and further there is cabinet combined the toughness and material or elastic material, is constructed by interlacing particle board and filament winding (see for example, Patent Document 4). Further example, is an example of viscous material in the cabinet, a large number of forms a porous air chamber by an elastic structure inside the cabinet as the use of an elastic material, filled with viscous material, volume increasing effect and sound absorption some purposes even but elastic structure use, of the viscous structure is also conducted (see for example, Patent Document 5). As for the frame of the loudspeaker unit, the suppression of vibration have sought, providing a reinforcing rib reinforcing the frame has also been (see for example, Patent Document 6). However, in a schematic diagram of the process of propagation of the vibration shown in FIG. 24, for the deformation of each place and vibration propagation emanating from the loudspeaker unit that occur at the same time sound comes out at the start of the first vibration, the current situation is hardly addressed comprehensively and fundamentally.
The adverse effect of vibration P5 coming from the cabinet, the adverse effect of action and reaction vibration P6, and the adverse effect to the vibrating cone due to the elasticity resistance with an air capacity of cabinet, for these three adverse effects, the analysis is further described. The additional vibration P5 to the back surface of the vibrating cone of the loudspeaker unit by the vibration of the cabinet wall and reflected sound from the cabinet wall is a big factor, as a means for reducing this, of the shown in FIG. 25, in the prior art arrangement are placed back and forth for the two loudspeaker units SP1 and SP2, is driven with the same phase to form a common sound chamber 6, isolate the adverse effects of the cabinet is known. Thus, in addition to eliminating the vibration of the rear vibrating cone to isolate the effect of the cabinet in common sound chamber 6, for two loudspeakers to operate in the same phase, the rear loudspeaker unit forms the state that is easy to vibrate for front loudspeaker unit SP. By two vibrating cones to operate in the same phase polarity, the common sound chamber is the noise cancellation state, regarded the cabinet vibration as a noise, at the same time in this state, it is also possible to see the back assist states of the vibrating cone operation of the front loudspeaker unit by the rear loudspeaker unit. Thus, if two of three adverse effects are manufactured enough in consideration of rigidity and a vibration suppression, it will go towards solution, however, in this arrangement, it has not been solved about the vibration P6 by the side of the loudspeaker magnet by the action and reaction of vibration of the vibrating cone of a loudspeaker unit, and also since two loudspeaker units operate in the same direction for the same volume, the action and reaction vibration P6 increases. There is a back-to-back arrangement for the two loudspeaker units to offset the solution of the vibration caused by the action and reaction, and there is a arrangement to emit a sound outside for both loudspeakers (see for example, Patent Document 7), and there is a arrangement to emits a sound inside of a cabinet for one side loudspeaker (see for example, Patent Document 8). The action and reaction vibration P6 headed in the direction of resolution, the arrangement to make this back-to-back will bring forward the playback of sound fine if you manufacture in consideration to damping, however, for the additional vibration P5 to the back surface of the vibrating cone of the loudspeaker unit and the vibrating cone vibration caused by the elasticity of the air cabinet, the adverse effect reduction has not been made.
Therefore, for the purpose of solving both at the same time, there is suggestion to be shown in FIG. 26. In the back-to-back two loudspeaker units operated in the same phase polarity, so offsetting the vibration of the magnet according to action and reaction, it is guided by the sound path from the rear portion sound of the front loudspeaker unit SP1 to the vibrating cone front portion of the rear loudspeaker unit SP2, sound path although the diffraction, to form a common sound chamber 6 between SP2 and SP1, as well as before and after arrangement of the loudspeaker in FIG. 25, and it is what led to the cabinet from the vibrating cone rear portion sound of the rear loudspeaker unit SP2 further (see for example, Patent Document 9). By the loudspeaker placement of back-to-back, the offset reduction of action and reaction vibration P6, due to the formation of common sound chamber 6 and isolation of the additional vibration P5 by cabinet due to noise cancellation state of common sound chamber 6, back assist by the rear loudspeaker unit has been conducted, if production in consideration to the damping and stiffness, the improvement of reality by the reproduction of the sound clear and crisp sound reproduction of the fine is confirmed.